Partial Slip Regime Research Articles

Partial-gross slip fretting transition of martensitic stainless steels

Based on critical reviews of the well-known dependence of fretting process upon the sliding amplitude, experiments were performed to verify this dependence. One of the main critical points is that the experiments which led to this result were performed controlling the imposed displacement amplitude instead of the real sliding amplitude. Therefore, the difference between the real displacement amplitude and the imposed amplitude due to compliances of the test rigs components was not considered.Fretting tests were performed using a high precision test rig. One of the main peculiarities of this test rig is that there is no difference between the imposed sliding amplitude and the real amplitude. The fretting process parameters of experiments were room temperature, two normal load (contact pressure 15, 25 MPa), four strokes (10, 15, 20, 50 μm), two martensitic stainless steels (X20Cr13, M152) and different durations from 15 to 160 M-cycles. Friction coefficient was computed using the hysteresis loops measured during the wear test. The worn surfaces were measured using an optical instrument based on focus variation. Wear volumes were accurately computed with a procedure that takes in to account the roughness of the surfaces.Results show that the friction coefficient is independent of slip amplitude, normal load and steel type if the hysteresis loops shape is parallelogrammatic and the contact surfaces are effectively conformal. When these conditions are not observed, the friction coefficient is dependent on normal load, even in contrast with its increase. Wear volume shows linear evolution in gross slip regime while it is non-linear in partial slip. Wear rate is independent of slip amplitude and normal load in partial slip regime at low ratio amplitude contact length. In contrast, wear rate depends on slip amplitude and exhibits a sharp increase near the transition partial-gross slip.

Real-time fretting loop regime transition identification using acoustic emissions

Acoustic emission (AE) has been successfully used to investigate the damage mechanisms of fretting contacts within different regimes. This study investigated the transition between fretting regimes using the relationship between AE and the mechanical response of a dry, steel-on-steel, ball-on-flat contact under different tangential displacements achieving the partial slip regime, mixed fretting regime and gross slip regime. Increased AE response occurred during gross-slip events and there was strong positive correlation between AE and fretting energy ratio. The relationship was strongest when gross sliding was experienced allowing identification of transition from the partial slip to the gross slip regime. This makes AE a good candidate to detect regime transition in-situ due to ease of integration and its non-destructive nature.

Investigation of crack initiation path in AA7050-T7451 under fretting conditions

Abstract Early crack orientation in 7050-T7451 aluminum alloy was investigated under fretting conditions. New tests were performed in the partial slip regime to observe the influence of the tangential load amplitude, mean bulk stress, and pad radius on the crack orientation. Three critical plane fatigue parameters were combined with different stress averaging methods to estimate the crack initiation direction. The normal stress-based Smith–Watson–Topper parameter provided better crack orientation estimates than the shear stress-based parameters. The experimental observations indicated a small increase in the early crack angle when the tangential load amplitude was raised.

Effect of load on the fretting behavior of SAF 2507 super duplex stainless steel in air and sea water

PurposeThis paper aims to study the influence of load and environment medium on the fretting behavior of SAF 2507 SDSS.Design/methodology/approachIn this study, the effect of load on the fretting behavior of SAF 2507 SDSS in air and sea water were studied. The fretting wear tests under different loads were conducted with a ball-on-flat contact configuration. The friction coefficient, wear volume, surface morphology and oxidation component were determined.FindingsWith the increase of applied load, the friction coefficient decreases both in air and sea water. The fretting mechanism is gradually transformed from partial slip regime to slip regime in air while the fretting counterparts are all in the state of gross slip in sea water. In sea water, the friction coefficient is lower while the wear loss is higher compared with that in air.Research limitations/implicationsThis research suggests that the fretting behavior of SAF 2507 SDSS is related to load and environment medium.Practical implicationsThe results may help us to choose the appropriate load under different environments.Originality/valueThe main originality of the research is to reveal the fretting behavior of SAF 2507 SDSS under different loads in air and sea water, which would help us to realize fretting behavior of SAF 2507 SDSS is controlled by the combination of applied load and lubricating environment.Peer reviewThe peer review history for this article is available at: http://dx.doi.org/10.1108/ILT-08-2019-0335.

Experimental investigations into fretting wear and damage mechanisms of Inconel X-750 alloy

Fretting wear characteristics of Inconel X-750 were investigated under the dry test condition. Ball-on-flat contact configuration was subjected to the oscillatory movement at different sliding amplitudes through the different time duration and normal loading. Fretting tests were carried out according to the American Society for Testing and Materials standards (ASTM D6425) by the high frequency linear-oscillation wear test rig SRV 4 at room temperature with ∼60 % relative humidity. Worn surface morphologies in the case of stick, partial slip and gross slip regimes were examined by 3D optical profiler, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The aim of this research is to study the tribological characteristics of the Ni-based Inconel X-750 superalloy, which is widely used in the air lubricated gas foil bearing applications where contacting surfaces are subjected to fretting motion. It is found that the displacement amplitude and normal load had strong effect on the fretting mode and damage mechanism. Wear mechanisms were associated with the plastically sheared asperities and crack nucleation and propagation during the stick and partial slip regimes, respectively. As the displacement increased, the wear modes were switched to adhesion, abrasion, debris oxidation, delamination and plastic deformation during the gross slip condition. Fretting time dependence was critical in the higher displacement amplitudes where the wear volume loss progressed significantly. However, test duration was less consistent in the stick and partial slip regimes where the wear properties remains unchanged over time.

Fretting Behavior of Thermoplastic Polyurethanes

Fretting tests were conducted with five different thermoplastic polyurethanes against a steel ball. Their fretting behaviors were investigated under various test parameters, such as normal load and displacement amplitude. In order to test the sliding performances, tribological tests were conducted using a ring-on-disc setup. The results show that their fretting behaviors can be related to the dynamic mechanical properties, which were characterized by dynamic mechanical analysis (DMA). The three fretting regimes were identified by means of hysteresis and wear scar analysis. In addition, investigations were carried out until the transition regimes occurred. Different wear processes were revealed for each of the three regimes. Differences were identified using dissipated energy. The profiles of wear scars and the counterparts were analyzed using a microscope. The coefficient of friction was calculated separately for the partial slip and gross slip regimes. In the mixed fretting regime, the coefficient of friction is almost at the same level among the five materials. In the partial slip regime, however, it can be distinguished. Temperature measurements were conducted on the counterparts during the tests. Overall, the material that showed the best tribological properties also performed the best in the fretting tests.

Fretting failure of a pressure armour in an unbonded flexible riser

In the present paper, the failure of a pressure armour in a flexible riser under fretting wear loading is analysed. Fretting lifetime is evaluated through the multiaxial fatigue criterion by Carpinteri et al., implementing the critical direction method proposed by Araujo et al. to define the orientation of the critical plane. The fretting map (in terms of number of loading cycles to failure against displacement amplitude) is build starting from the simulation results of some fretting wear tests in partial slip regime. Then, such a map is compared with that determined by means of the results derived through a combined experimental and numerical methodology available in the literature.

Study on tribo-chemical and fatigue behavior of 316L austenitic stainless steel in torsional fretting fatigue

Fretting fatigue is a complex tribological phenomenon that can cause premature failure of connected components. Combining with the effects of tribological and fatigue, the components have premature fracture, which ultimately leads to disastrous consequences. In this work, the fretting fatigue tests of 316L austenitic stainless steel have been carried out with same normal load and varied torsional torques. The results indicate that the fretting fatigue life significantly depends on the torque amplitude, wear degree of the fretting damage zone, hysteresis loops and energy dissipation. A physical model for fretting crack initiation and propagation is created to explain the failure process of torsional fretting fatigue. The results from X-ray photoelectron spectroscopy analysis show that the extent of oxidation in the fretting damage zone is affected by the amplitude of relative displacement. The tribo-chemical reaction in the slip regime is more activated than that in partial slip regime. It can lead to more severe wear in the slip regime. The wear debris of the fretting damage zone is composed of metallic Fe, Fe2+ and Fe3+.

Understanding the microstructure evolution of Ni-based superalloy within two different fretting wear regimes in high temperature high pressure water

The microstructure evolution of the worn scar central areas formed on Ni-based Alloy 690 (Ni–30Cr–10Fe, wt%) within two different fretting wear regimes in high temperature high pressure (HTHP) water were studied in detail by high resolution characterization techniques. A very complex stratified structure was found within gross slip regime while only a relatively simple structure was found within partial slip regime. The wear mode and the evolution mechanisms of specific microstructures within the two different fretting wear regimes are clarified.

Investigation on the Fretting Wear Behavior and Mechanisms of Alloy 690TT during the Transformation from Mixed Regime to Partial Slip Regime Induced by Elevated Temperature

Fretting wear of Alloy 690TT can occur in the steam generator of a nuclear power plant, in which the interfacial conditions are changed as the temperature varies. In this study, the gradual transformation from the mixed fretting regime (MFR) to the partial slip regime (PSR) occurred with an increase in test temperature. Correspondingly, there was a competition in wear modes due to the formation of a nanostructured tribologically transformed structure (TTS), presence of delamination cracking, nucleation of fatigue cracks, and oxidation. Delamination within the TTS dominated first. As the area of TTS and the plastic deformation region was reduced, fatigue cracks began to initiate. Oxidation was accelerated by an increase in the test temperature, and that effect resulted in reduced wear volume of Alloy 690TT in the MFR.

Torsional fretting corrosion behaviours of Ti6Al4V alloys in Hank’s simulated body fluid

ABSTRACTTorsional fretting corrosion in a physiological medium is one of the main reasons that artificial joints fail. In this study, we carried out experiments on torsional fretting corrosion in Titanium alloys (Ti6Al4V) against Zirconium dioxide (ZrO2) ceramic balls under 37°C in a Hank’s simulated body fluid. During the tests, we recorded electrochemical corrosion parameters using an electrochemical analysis system in real-time. We analysed the torsional fretting dynamics behaviours, damage mechanisms, and electrochemical corrosion behaviours in detail using the micro-examinations of a scanning electron microscope (SEM), an energy-dispersive X-ray (EDX), a profilometer, and an X-ray photoelectron spectrometer (XPS). The results showed that the dynamics behaviours strongly depended upon the torsional angular displacement amplitude and the number of cycles. The friction torque increased with increases in the torsional angular displacement amplitude and normal load. We established a running condition fretting map (RCFM), which included three fretting running regimes: a partial slip regime (PSR), a mixed fretting regime (MFR), and a slip regime (SR). We determined that the influences of torsional fretting on electrochemical corrosion behaviours were strongly correlated to the angular displacement amplitude. Under large angular displacement amplitudes, the corrosion of the Ti6Al4V alloys in Hank’s simulated body fluids were accelerated by torsional fretting, especially during the initial stage of the test. However, when the angular displacement amplitude was smaller than 1°, the corrosion potentials and corrosion currents were almost invariable during the entire duration of the test. The damage to the Ti6Al4V alloy was the result of wear and corrosion. The wear mechanisms were attributable to delamination and abrasive wear in the three fretting regimes. We observed almost no damage on the contact centre and only slight scratches and wear on the contact edge in the PSR. In MFR testing, the damage zone extended to the contact centre and the sticking zone (which exhibited no damage) contracted to the contact centre with increases in the number of cycles. Ultimately, in MFR and SR testing, the damage mechanisms were primarily the result of abrasive wear, oxidation wear, tribochemical reactions, adhesion wear, and electrochemical corrosion.

Fretting Wear Behavior and Damage Mechanisms of Inconel X-750 Alloy in Dry Contacts

Tribological behavior of the Inconel X-750 alloy disk subjected to fretting against the GCr15 steel ball was investigated in an ambient laboratory air with relative humidity of 55–65%. A high-frequency oscillating Optimol SRV 4 tribometer was employed to execute dry fretting tests in the partial and gross slip regimes under constant 100 N normal load. Tests were carried out for 10, 30, and 90 minutes, and the friction forces vs. displacement amplitudes were monitored during the test duration. Posttest examinations were conducted utilizing advanced tools such as 3D optical surface profiler, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The main objective was to obtain wear scar evolutions, frictional properties, and degradation mechanisms under the different running conditions over time. It was found that fretting wear behaviors of friction pairs were strongly influenced by fretting regimes. Degradation evolutions were greatly influenced by fretting time during partial slip regimes, i.e., evolving from asperity deformation and slight damage to the fatigue crack and material transfer. However, the combination of adhesive, abrasive, delamination, and wear oxidation mechanisms was repeated during the entire gross slip fretting process.

The Effects of Sodium Chloride Solution on Fretting Wear Behavior of Nickel Based Alloy in Partial Slip Regime

The investigations on fretting wear behaviors of nickel based alloy in NaCl solution and atmosphere indicated that wear mechanism and regional transformation from partial slip regime (PSR) to the mixed regime (MR) are significantly affected by NaCl solution. The crevice corrosion induced by synergy of chloride ion and deformed asperities caused wear mechanism changed from adhesive and oxidation wear (PSR in atmosphere) to abrasive and oxidation wear (PSR in NaCl solution) and to oxidation and delamination wear (MR in NaCl solution), meanwhile accelerated the regional transformation from PSR to MR. However, the annular fatigue crack was almost unaffected by NaCl solution, which propagated along the direction of 40-50° to surface in the mode of transgranular and intergranular in all conditions.

Effect of Cold Rolling on the Fretting Wear Behavior and Mechanism in Inconel 690 Alloy

The influence of cold rolling on the fretting wear behavior and mechanism of Inconel 690 alloy at 320 °C in air was studied. The wear volume and worn surface were obtained and analyzed using laser scanning confocal microscopy, electron back-scattering diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The grinding surface and strain distribution were also studied by electron back-scattering diffraction to analyze the mechanism of fretting damage. The results indicated that with an increase in cold rolling reduction, the microhardness was increased. However, the friction coefficient and wear volume first increased and then decreased. The characteristics of fretting areas changed from a gross slip regime to a partial slip regime. Accordingly, the damage mechanism in the gross slip regime was a combination of oxidative wear, abrasive wear, and delamination, whereas the damage mechanism in the partial slip regime was mainly adhesive wear.

Experimental Method of Tribological Modelling of Different Coatings of Stainless Steel

Abstract Fretting wear is a unique form of material degradation caused by small amplitude oscillatory relative motion of two surfaces in contact. Fretting wear is typically encountered at relative displacements of less than 300 μm and occurs in either a gross slip regime [1] (where there is slip displacement across the whole contact), or a partial slip regime (where there are parts of the contact where no slip displacement occurs). Fretting wear is experienced within a wide range of industrial sectors, [2] including aero engine couplings, locomotive axles and nuclear fuel casings [3]. Under higher loads and smaller displacement amplitudes, the contact will be within the partial slip regime, often resulting in fretting fatigue where the dominant damage mode is a reduction in fatigue life [4]. Friction is a very common phenomenon in daily life and industry, which is governed by the processes occurring in the thin surfaces layers of bodies in moving contact. The simple and fruitful idea used in studies of friction is that there are two main non-interacting components of friction, namely, adhesion and deformation [5, 6].

Comparative study on fretting wear behaviors of Alloy 600MA in dry air and deionized water conditions

Fretting wear behaviors of Alloy 600MA in dry air and deionized water conditions were investigated. Results indicated that partial slip regime (PSR) and gross slip regime (GSR) were separated in running condition fretting map (RCFM). In deionized water, the boundary of PSR/GSR shifted into lower amplitude. In material response fretting map (MRFM), the cracking and particle detachment were characterized. In dry air, white etching layer (WEL) transformation resulted in the crack propagation in PSR and the formation of wear debris layer (WDL) in GSR. In deionized water, WEL was more difficult to be formed, resulting in shorter crack and smaller thickness of WDL. In nanostructured WDL, there were non-stoichiometric oxides of NiO, (Ni,Fe)(Fe,Cr)2O4 and Cr2O3 for dry air. The unoxidized phase of (Ni, Cr, Fe) coupled with non-stoichiometric oxides existed in WDL for deionized water.

Torsional Friction Behavior of Contact Interface Between PEEK and CoCrMo in Calf Serum

Polyether ether ketone (PEEK) and its composites are recognized as alternative bearing materials for use in arthroplasty because of their excellent mechanical properties. In this paper, torsional friction tests of PEEK against the CoCrMo alloy, simulating the contact mode between the prosthesis tibia and femur, were carried out under a 25% calf serum solution in a Leeds Prosim knee simulator. The torsional friction behavior of PEEK against the CoCrMo alloy was investigated under various normal loads (1000 N, 1600 N and 2200 N), torsional angular displacement amplitudes (±1 deg, ±3 deg, and ±5 deg), and the number of cycles (7500, 15,000, and 30,000). The torsional friction characteristics and damage mechanism are discussed. The results show that PEEK exhibited low friction coefficient under the different conditions. With increases in the torsional angle and normal load, three types of torque/angular displacement amplitude (T–θ) curves (i.e., linear, parallelogram, and elliptical loops) were observed and analyzed during the process of torsional friction. With the increase of the torsional angle, the coefficient of friction decreases. And the contact states change from the partial slip regime to the slip regime. The greater the torsional angle displacement, the more severe the damage to the PEEK surface. With an increase in the normal load, the wear scars increased. The wear depth is deepened and the width is widened, and the wear gradually becomes serious with an increase in the load. The small load is more likely to cause damage to the central area of PEEK, and the larger load causes more serious damage to the marginal region. The central and marginal regions of the PEEK sample have different wear characteristics. The worn surfaces of the central regions were characterized by convex ridges resulting from plastic deformation, while curved ploughs and fatigue peeling appeared in the marginal region. The wear mechanism of PEEK in the central region is plastic deformation, while fatigue wear and abrasive wear mainly appeared in the marginal region.

Fretting wear behavior of Ti/TiN multilayer film on uranium surface under various displacement amplitudes

Abstract Ti/TiN multilayer film was deposited on uranium surface by arc ion plating technique to improve fretting wear behavior. The morphology, structure and element distribution of the film were measured by scanning electric microscopy (SEM), X-ray diffractometry (XRD) and Auger electron spectroscopy (AES). Fretting wear tests of uranium and Ti/TiN multilayer film were carried out using pin-on-disc configuration. The fretting tests of uranium and Ti/TiN multilayer film were carried out under normal load of 20 N and various displacement amplitudes ranging from 5 to 100 μm. With the increase of the displacement amplitude, the fretting changed from partial slip regime (PSR) to slip regime (SR). The coefficient of friction (COF) increased with the increase of displacement amplitude. The results indicated that the displacement amplitude had a strong effect on fretting wear behavior of the film. The damage of the film was very slight when the displacement amplitude was below 20 μm. The observations indicated that the delamination was the main wear mechanism of Ti/TiN multilayer film in PSR. The main wear mechanism of Ti/TiN multilayer film in SR was delamination and abrasive wear.

Oil-Lubricated Fretting Behaviors of 304 Stainless Steels under Different Fretting Strokes and Normal Loads

ABSTRACT The influence of oil lubrication on the fretting wear behaviors of 304 stainless steel flat specimens under different fretting strokes and normal loads has been investigated. The results proved that fretting regimes and fretting wear behaviors of 304 stainless steels were closely related to the fretting conditions. In general, the increase in normal load could increase wear damage during sliding wear. However, according to the results, a significant reduction in wear volume and increase in friction coefficient was observed when the normal load was increased to critical values of 40 and 50 N at a fretting stroke of 50 μm due to the transformation of the fretting regime from a gross slip regime to partial slip regime. Only when the fretting stroke further increased to a higher value of 70 μm at 50 N, fretting could enter the gross slip regime. There was low wear volume and a high friction coefficient when fretting was in the partial slip regime, because oil penetration was poor. The wear mechanisms were fatigue damage and plastic deformation. There was high wear volume and low friction coefficient when fretting was in the gross slip regime, because the oil could penetrate into the contact surfaces. Unlike the wear mechanisms in the partial slip regime, fretting damage of 304 stainless steels was mainly caused by abrasive wear in the gross slip regime.

Effect of displacement amplitude on fretting wear of 304 stainless steel in air and sea water

AbstractThe fretting wear behaviours of 304 stainless steel at different displacement amplitudes were investigated by using a SRV‐IV fretting tester in air and sea water, respectively. In air, the friction coefficient as well as the fretting damage of 304 stainless steel increased with the increase of displacement amplitude, and the fretting regime changed from partial slip regime to gross slip regime. Correspondingly, the wear mechanisms transformed from local fatigue and slight oxidation to the combination damages of adhesion wear, abrasive wear, and oxidation. Compared with the dry friction conditions, sea water had a strong effect on fretting behaviour of 304 stainless steel. Adhesion wear was effectively suppressed due to the cooling and lubrication effect of sea water. Therefore, friction coefficient and wear depth decreased significantly. And the damages of 304 stainless steel in sea water were mainly caused by abrasive wear, slight adhesion wear, and corrosion wear.